1. Field of the Invention
The present invention relates to an improvement of an apparatus for operating a cage of an elevator at an emergency such as power stoppage.
When the cage of the elevator is stopped between floors at an emergency such power stoppage, passengers are uneasy and frightened because they are kept in the cage. In order to prevent such condition, an AC traction motor is driven by a DC power source such as a battery or an inverter device in the case of the AC elevator to operate the cage so as to stop on a nearest floor to escape from the cage.
2. Description of the Prior Arts
The apparatus shown in FIG. 1 has been known. In FIG. 1, the references R, S, T designate a three phase DC power source for 400 V; (1a) to (1c) designate contacts of a contactor for ascending operation which are closed for the ascending operation of the cage (not shown) in the normal state; (2a) to (2c) designate contacts of a contactor for descending operation which are closed for the descending operation of the cage on one group of the contacts (1a) to (1c) of the contactor for the ascending operation or the contacts (2a) to (2c) of the contactor for the descending operation is closed. (This is referred to as interlock). The reference (3) designates a traction motor as an induction motor having a rated voltage of 400 V which drives the cage; (4) designates the DC power source such as a DC battery; (5) designates a contact for a contactor for an emergency operation which is closed during the emergency operation; (6) designates an inverter comprising semiconductor devices for converting the DC power force into the AC power force; (7) designates an oscillation circuit for generating the pulse for determination of the output frequency of the inverter device (6); (8) designates a turn-on circuit for generating a turn-on signal for sequentially turning on elements of the inverter device (6) by receiving the output pulse of the oscillation circuit (7) as the input; (9a) to (9c) designate contacts of a contactor for the ascending operation which are closed for the ascending operation of the cage in the emergency operation; (10a) to (10c) designate contacts of a contactor for the descending operation which are closed in the descending operation; and the contacts (9a) to (9c) and (10a) to (10c) are respectively interlocked with each other and also interlocked to either of the contacts of (1a) to (1c) or (2a) to (2c) the contactors for the ascending operation or the descending operation as to be interlocked. An AC motor for door-opening and closing (not shown) can be connected. In the normal state, the AC power of the three phase AC power source R, S, T is fed through the contacts (1a) to (1c) or (2a) to (2c) of the contactor for the ascending operation or the descending operation to the traction motor (3) whereby the cage is driven. In the emergency state, the contact (5) of the contactor for emergency operation is closed whereby the AC power having a specific frequency converted by the inverter device (6) is fed through the contacts (9a) to (9c) or (10a) to (10c) of the contactor for the ascending operation or the descending operation, to the traction motor (3) whereby the cage is driven.
When the induction motor is driven by the inverter device (6), the following equation is usually given in view of the phenomenon of magnetic saturation and the torque. EQU V/f.apprxeq.V'/f'
wherein
V: voltage of the power source in the normal state;
f: frequency of the power source;
V': output voltage of the inverter device (6);
f': output frequency of the inverter device (6).
Therefore, when the traction motor (3) is driven, the output frequency f' and voltage of the battery are set to the suitable values in view of the speed and cost required for the emergency operation.
When an induction motor is used for a motor for door-opening and closing of the cage, sometimes the rated voltage of the traction motor (3) is different from the rated voltage of the motor for door-opening and closing. The voltage of the power source for the traction motor (3) is 400 V in three phase whereas the voltage of the power source for the motor for door-opening and closing is 100 V in three phase. In view of the above equation and the revolution speed of the motor for door-opening and closing, it is necessary to use a separate circuit for the motor for door-opening and closing then that shown in FIG. 1. Such feature has not been advantageous in view of the complicated circuit, the cost and equipments and the reliability.